This invention is concerned with submergible pump installations, and more particularly with a submergible pump having a discharge head that automatically locks into a well liner.
The present invention is an improvement upon the invention disclosed and claimed in U.S. Pat. No. 3,853,430, issued Dec. 10, 1974, assigned to the same assignee as this invention, and incorporated herein by reference. The prior patent discloses a cable-suspended, submergible electric pump installation in which the pump discharge head has a locking device for locking the discharge head to a well liner, so that the pump installation cannot be dislodged by bottom hole pressure. The locking device employs generally cylindrical rollers which are cammed outwardly beneath a shoe at the lower extremity of the liner when an outer member of the discharge head seats in the liner and an inner member continues to move downwardly. The discharge head employs seals between the inner and outer members to isolate the locking rollers from the high pressure discharge of the pump, in addition to external seals between the outer member and the liner shoe. Pins fixed to the outer member extend into longitudinal grooves on the inner member to prevent rotation of one member relative to the other. In the commercial embodiment of this apparatus, rotation between the outer member and the liner is prevented by mutually engaging teeth on the outer member of the discharge head and a shoulder of the liner.
The foregoing apparatus provides many advantages over earlier submergible pump installations, particularly in the ability to prevent unseating of the pump installation by bottom hole pressure. However, the rollers used as the locking elements are hard to contain and serve only as locking elements. The entire weight of the pump installation and the column of pumped fluid is supported by an internal shoulder of the liner, so that the internal diameter of the liner is limited by the need for providing a shoulder wide enough to carry the load. Special elements must be provided to resist the torque produced when the pump is operated that tends to cause rotation between the inner and outer members of the discharge head. Multiple O-ring seals are employed, and these lack resistance to abrasive materials found in many wells.